A direct current (DC)-to-DC converter converts a DC input voltage to a desired DC output voltage. A buck converter is a type of DC-to-DC converter in which a controller individually toggles on and off a pair of transistors serially connected between power and ground to deliver charge to an inductor, and through the inductor to a capacitor. In order to preserve efficiency, some DC-DC converters adapt to different load conditions. Some DC-to-DC converters are configured to distinguish light-load and high-load conditions. Under high-load conditions, a buck converter may operate in a “continuous” operating mode in which the one or the other of the pair of transistors is on at all times. Under light-load conditions, some buck converters enter a “discontinuous/pulse frequency” operating mode. In the discontinuous/pulse frequency operating mode, the DC-DC converter becomes active when the output voltage falls below a certain threshold voltage level. During the discontinuous/pulse frequency mode, the inductor current falls to zero during a part of each cycle in which neither transistor is on. Buck converters may change from the continuous operating mode to the discontinuous/pulse frequency operating mode when load current reduces sufficiently. When load current increases, the converter may switch back to the continuous operating mode.